(a) Field of the Invention
The present invention relates to a liquid crystal display having wide viewing angle.
(b) Description of the Related Art
A liquid crystal display (LCD) includes two substrates and a liquid crystal layer interposed therebetween. The transmittance of the light is controlled by the strength of the electric field applied to the liquid crystal layer.
A conventional twisted nematic (TN) liquid crystal display, which is one of the most widely used LCD, has a couple of transparent substrates which have transparent electrodes respectively on their inner surfaces, a liquid crystal layer between two substrates, and a couple of polarizers which are attached to the outer surfaces of the substrates respectively. In off state of the LCD, i.e., in the state that the electric field is not applied to the electrodes, the long axes of the liquid crystal molecules are parallel to the substrates and twisted spirally with a constant pitch from the inner surface of one substrate to that of the other substrate, and thus the orientation of the long axes of the liquid crystal molecules vary continuously.
However, the contrast ratio of the conventional TN LCD in a normally black mode may not be so high because the incident light is not fully blocked in its off state, i.e., in absence of the electric field.
To solve this problem, a vertically aligned twisted nematic (VATN) mode LCD is proposed in the U.S. Pat. No. 3,914,022 and in "Eurodisplay '93", pp. 158-159 by Takahashi.
The VATN in normally black mode may have an off state which is sufficiently dark, because the liquid crystal molecules are aligned perpendicular to the substrates in off state. However, the viewing angle of the VATN LCD may not be so wide.
On the other hand, T. Yamamoto et al. disclosed a VATN simple matrix LCD using fringe fields in "SID '91, pp. 762-765", and Lien proposed a structure having an aperture in the pixel electrode to solve the problem of low transmittance in on state of a simple matrix multi domain VATN.
However, the structure that Lien proposed, may have light leakage generated near the aperture.